1. Field of the Invention
The present invention relates to a method of preserving foods using noble gases.
2. Description of the Background
Gas packaging of foods for preservation is well known, and a general description of this technique may be found in A. L. Brody, Controlled/Modified Atmosphere/Vacuum Packaging of Foods, Food and Nutrition Press, Trumbull, Conn. 01989. A description of important consumer quality perception parameters is presented in J. J. Jen, Quality Factors of Fruits and Vegetables, Chemistry and Technology, ACS Symposium Series No. 405, American Chemical Society, Washington, D.C., 1989, and a description of the biochemical and chemical reactions important in foods may be found in N. A. Michael Eskin, Biochemistry of Foods, second ed., Academic Press, New York N.Y., 1990.
It is evident from these sources that a large preponderance of modern and past gas packaging methodologies have relied primarily upon the use of carbon dioxide, nitrogen, and oxygen, alone or in mixtures. Generally, nitrogen is used as an inerting; or non-reactive gas, to displace oxygen in order to prevent oxidation or limit respiration. Generally, carbon dioxide is used as a microbiocidal or microbiostatic agent, or as in the case of certain beverages, to provide an effervescent effect. Carbon dioxide is also often used as an inerting gas. Generally, oxygen is used as such or as the active component in the inclusion of air to permit aerobic respiration or to prevent the development of anaerobic conditions which might permit the growth of pathogenic microorganisms.
For example, U.S. Pat. No. 4,454,723 describes a refrigerated trailer cooled by sprinkler water with concomitant release of inerting nitrogen from a cryogenic source, for inerting the respiration of produce.
CH 573848 also describes the inerting activity of nitrogen in the preparation of coffee packages.
Irisawa, 1974, describes the use of a nitrogen atmosphere or liquid in the preservation of strawberries, salmon, and fish.
Kocys and Veskevicius, 1970, describe the storage in nitrogen.
Lapin and Koburger, 1974 describe the storage of shrimp in N2, showing improved control of bacteria.
Moor, 1984 describe storage of malting barley in a N2 atmosphere.
Niu and Su, 1969, describe effective storage of bananas in N2.
Lebedeva et al., 1984, describe the utility of nitrogen in storage of sunflower seeds preserved in a nitrogen atmosphere as due to a change in oxidative metabolism, that is, respiratory rates.
U.S. Pat. No. 4,515,266 exemplifies the importance of package type in gas packaging applications. A modified atmosphere packaging high barrier film is used in the packaging, and a preservative atmosphere is introduced into the package. The essence of the packaging process is that it allows preservative gases, such as nitrogen gas for inerting, to be introduced, but at the same time prevents air from getting into the package which would allow oxygen to contact the food and which would then cause degradative oxidation of the food product.
U.S. Pat. No. 4,522,835 shows that gases whose molecules contain oxygen can often be reactive in food systems, herein including oxygen, carbon dioxide and carbon monoxide. Preservation of color in poultry, fish is claimed by reducing oxygen content to produce myoglobin/hemoglobin versus the ordinary oxidized states of oxymyoglobin/hemoglobin, and finally adding carbon monoxide to produce carboxymyoglobin/carboxyhemoglobin, then storing under carbon dioxide to maintain the thus improved color. Storage under inert nitrogen is possible, as is further reoxidation using oxygen.
EP 354337 claims the use of carbon dioxide as an antibacterial agent in the preservation of foods.
SU 871363 illustrates the complexity of gas packaging methodologies, as specific regimes of preparation and gas applications are often recommended. This patent describes the storage of plums in nitrogen, oxygen and carbon dioxide mixtures in three separate steps. 1st, 2-2.5 wks at 0xc2x0 C. in 78-82% nitrogen+10-12% oxygen+8-10% carbon dioxide; 2nd, for next 2.5-3 wks at xe2x88x921xc2x0 C. in 93-95% nitrogen+3-5% oxygen+2-4% carbon dioxide; 3rd, remainder of storage period at xe2x88x922xc2x0 C. in 90-92% nitrogen+2.5-3.5% oxygen+4.5-5.5% carbon dioxide. The method claims 99.4 vs 91-94% good condition after 151 days. This marginal increase may be considered to be due primarily to more effective regulation of the respiratory gas exchange between oxygen and carbon dioxide, where nitrogen plays no real part except as an inert bond non-reactive carrier gas.
SU 1245284 reinforces such concepts of treatment. Here cherries are better kept under a limiting respiratory mixture of carbon dioxide 5-8%+oxygen 4.5-5.5%+nitrogen bal. It is important that the fruit be picked at the correct maturation stage, and kept chilled at 0 to xe2x88x921xc2x0 C., also to lower respiration.
WO 9015546, CA 2019602, AU 9059469 each describes the importance of the climacteric state of foods, that is the ethylene-induced maturation phase of the product. Each discloses improved preservation of food in a process using two gas separators, where first, unwanted gases, such as ethylene, oxygen, carbon dioxideand water vapor are removed, second, the preservative (inert or respiratory mix) gas is supplied.
JP 55029426 use a complex mixture of 20-99.5% nitrogen and/or carbon dioxide+80-0.5% ethanol vapor where residual oxygen is 10%. In an impermeable package, this is claimed to prevent sticky-substance forming fungi growth.
Burgheimer et al., 1967 provides evidence of the chemical changes which occur during exposure to oxygen, here spinach in air versus in a controlled atmosphere of nitrogen undergoes considerable degradative changes in vitamin C and ascorbic acid contents.
Similarly, Consignado et al. 1976 compare the sugar content of stored coconuts under air versus nitrogen, and find that sugar content is not surprisingly correlated with availability of oxygen for respiration.
Thus, it is evident that the gases oxygen, carbon dioxide, and nitrogen alone or in mixtures have the well-established effects of oxidation, antimicrobial activity, and inerting, repectively. It is also evident that the balance of such gases in an atmosphere superimposed upon living systems may depress respiration and the resulting production or maintenance of chemical and other food quality parameters in basic and well-understood ways. It is also evident that oxidative and reactive gases will have destructive effects upon chemical and biological systems.
Although literature has appeared describing the use of argon for packaging, this literature generally describes the gas to be completely inert and equivalent to nitrogen or the other noble gases in their non-reactivity.
It is also clear from the following literature citations that argon is typically described or used as an inert or non-reactive gas equivalent not only to nitrogen and the other noble gases, but that carbon dioxide, nitrous oxide and hydrogen and other gases are considered inert as well. This is particularly the case for food gas packaging systems.
For example, JP 2010077 describes the use of a mixed gas source to supply a gas packaged product with a mixture of nitrogen:carbon dioxide:ethylene 60:30:1 where the small amount of argon present is inert.
Also, JP 3058778 (89192663) describes storage and maturation of alcoholic drinks in an argon headspace. Deterioration can be prevented and maturation can be promoted or delayed by regulating the packaging density of argon. The utility of the argon lies in its displacement of oxygen, i.e., inerting.
JP 58101667 (88019147) describes sealing of citrus drink in vessels under pressure using an inert gas such as argon, so that bubbles are released upon opening which then cling to pulp.
JP 60134823 discloses a process whereby packaging of liquid food by is accomplished by feeding sterile liquid into the package under pressure with an inert gas, either nitrogen or argon.
JP 62069947 (88051660) discloses long term preservation of shiitake mushrooms in the dark in a container in a mixture of nitrogen:carbon dioxide:argon:nitrous oxide. Argon is described therein as an inert gas.
JP 63273435 describes preserving roasted chestnuts in a permeable container in a mixture of argon, carbon dioxide, nitrogen and nitrous oxide. The container is permeable to argon, therefore, it can have no utility.
JP 7319947 (730618) claims fruit juice preservation with noble gases. However, argon, helium and nitrogen are described as inert gases.
JP 77027699 describes a process for freezing and storing under pressure, the pressure being applied as carbon dioxide or nitrogen or argon or hydrogen, all being considered equally inert.
U.S. Pat. No. 4,054,672 (JP 7169757) describes the defrosting of frozen foods under a pressure of 2-5 atmospheres, preferably under carbon dioxide or nitrogen or helium or argon, all being inert, non-reactive and non-oxidizing.
JP 89192663 claims preservation of alcoholic beverages with argon, specifically sake and wine in containers, wherein argon is considered as a superior inerting agent due to its higher solubility than nitrogen.
U.S. Pat. No. 3,096,181 describes a food processing method and apparatus used in gas-packaging of tomato juice or liquid food products or vegetable concentrates, wherein any inert gas from the group of nitrogen, argon, krypton, helium, or mixtures thereof, are equally inert and useful at or above ambient pressure, after steam sterilization.
U.S. Pat. No. 3,128,188 describes lagering Ruh beer under an inert atmosphere.
U.S. Pat. No. 3,442,657 claims the preservation of hops in an inert atmosphere.
U.S. Pat. No. 3,498,798, CA 867629 describe a package for potato crisps which is impermeable and in which an inert gas is used to displace oxygen as the functionally useful step. It is disclosed that any of nitrogen or carbon dioxide or argon or neon may be used equivalently.
U.S. Pat. No. 3,535,124 discloses a process for fresh fruit juice preservation in a dispenser using carbon dioxide, wherein preferably the juice is sprayed through an inert atmosphere.
U.S. Pat. No. 3,587,203 describes the gas packaging of tossed salad cut and prepared ready to eat, where it is stored in an inert atmosphere in order to prevent oxidative discoloration.
U.S. Pat. No. 3,715,860 describes a method of gas packaging wherein inert fluid passage through an impermeable container functions to remove oxygen and prevent spoilage.
U.S. Pat. No. 4,152,464 describes a method and apparatus to sterilize packages which includes applying sterile any inert gas into an enclosed space.
U.S. Pat. No. 4,205,132 describes the storage of lyophilized bacteria. Storage requires the complete absence of oxygen, preferably using argon inerting because argon commercially contains very low levels of oxygen.
U.S. Pat. No. 4,229,544 describes the storage of dormant living microorganisms by gas packaging in nitrogen, argon or helium, where all are equivalent.
U.S. Pat. No. 4,391,080 describes a gas packaging machine in which the essence of the invention is the filling of the package through the machine with sterile inert gas.
U.S. Pat. No. 4,524,082 describes the preparation of concentrated egg white or salted whole egg product under inert atmospheres.
U.S. Pat. No. 4,627,336 also describes a gas packaging apparatus which requires the flushing of inert gases to replace air.
In U.S. Pat. No. 4,803,090, which concerns the preparation of cheese puffs in hot oil, it was not noticed that different inert gases produce any difference in the product.
Also, U.S. Pat. No. 4,835,937 describes a food packaging process involving flushing and filling with inert gas.
A similar process is claimed in U.S. Pat. No. 4,870,801.
U.S. Pat. No. 4,901,887 claims a beverage dispenser which is pressurized with an inert gas.
In U.S. Pat. No. 4,919,955 a gas packaging method for meat is described wherein inert gas is used to package and store the meat, and at a later stage oxygen is added to the package to permit oxygenation of the myoglobin to produce a red color.
Cooling of foods by direct injection of gases is described in DE 2147880, ZA 7106193, FR 2107946, GB 1371027, where any of nitrogen, oxygen, argon, or even Air may be used equivalently.
DE 2736282, WO 7900092, HU H2477, GB 2021070, DD 137571, DD 137571, EP 6888 describe a beer tank road tanker charging system which uses inert gas constituting any of carbon dioxide, nitrogen, or noble gas.
A process is claimed in EP 146510, SE 8306164, NO 8404468, FI 8404402, DK 8405347 for extrusion of porous foodstuffs by compression, heating and extrusion in an inert atmosphere, e.g. nitrogen or carbon dioxide.
EP 289777, AU 8814003, JP 1020056, U.S. Pat. No. 4,895,729 claim the packaging of cut or segmented fresh fruit pieces by flushing with O2-containing gas, sealing, cold shocking, refrigerating, wherein the preferred mixture is 5-50% oxygen and the balance is any inert gas from the group nitrogen, helium, argon or hydrogen.
BE 881368, DE 2903300, NL 8000353, GB 2042320, FR 2447155, U.S. Pat. No. 4,289,148, CA 1127037, CH 642519, NL 177974, IT 1130237 describe the improvement of packing capacity of tobacco by applying pressure using either nitrogen or argon then heating.
The pressurization of foods by sterile heat, followed by inert gas packaging is claimed in EP 368603, using either nitrogen or carbon dioxide. The factors of importance are water and oxygen content.
ES 8500634 discloses a method of vinification without using preservatives, using inert or non-reactive gas to displace oxygen to prevent aerobic microbial growth. Any of nitrogen, carbon dioxide, or the noble gases are deemed equally useful.
GB 1331533, FR 2089899, BE 765637, DE 2031068, CH 522734 describe a method of improving the keeping properties of alcoholic beverages produced by fermentation which prevents the destructive action of oxygen by displacing oxygen during or after fermentation and/or at any process stage and/or during storage under preferably nitrogen, but Ar or other noble gases may be used, all being equivalently inert.
IT 1190200 describes the use of an inert gas atmosphere upon agricultural products to prevent attack by aerobic microorganisms.
SU 249965 describes storage of brined meat e.g. ham under e.g. Ar as an inerting process.
SU 825619 describes a tank for storing wine in inert gas atm with filling controls. First the tank is filled with carbon dioxide, then wine is fed by pump or inert gas sprayer.
WO 8600503, DE 3425088, AU 8546026, EP 189442, DE 3448380 each disclose use of gas in the heating of liquid food products while maintaining pressure to prevent loss of aroma and prevent boiling. For milk and coffee prods, especially an inert gas and non-reactive such as nitrogen or a noble gas.
FR 2225095 describes the gas packaging of roasted coffee where the coffee is degassed in inert and non-reactive gas, preferably carbon dioxide, for 12-48 hrs, impermeable packets are filled with the coffee, a 50-90% partial vacuum is drawn, followed by injection of a preservative gas, where either argon or nitrogen at preferably less than  less than 1 atm may be used equivalently. The effectiveness of such inerting is claimed as a ten-fold improvement in shelf life.
In FR 2621224 for avocado pulp or other, the grinding in inert gas, followed by adding other flavoring food product liquids is claimed.
Storage of refrigerated butter under an inert atmosphere is claimed in FR 2642275, where the gas may be nitrogen or others.
Rzhavskaya 1967 describes the utility of nitrogen in preventing oxidation of whale fats due to displacement of oxygen.
Shejbal, 1979a,b describes the use of nitrogen in preservation of cereals and oilseeds by inerting.
Terebulina et al., 1983 describes lipid oxidation of rice in air as controllable by displacement of oxygen to prevent repiration and oxidation.
Corey et al., 1983, in addressing storage issues, measured nitrogen and carbon dioxide diffusion rates through cucumber and found carbon dioxide was three times as soluble as nitrogen. Solubility was determined to be the critical factor in storage atmosphere choice. Argon was used as an inert gas control.
Fullerton et al., 1982 show improvement in storage of animal feeds under argon as inerting agent because of its solubility and lack of oxygen content.
Pichard et al., 1984 tested the enzymes of bacteria, specifically Pseudomanas proteases under carbon monoxide, carbon dioxide and nitrogen. Air and Ar as mixers and controls. Only carbon dioxide was found to have effects, which conflicted depending upon which protease was measured, and argon was specifically found not to have an effect on these enzymes.
Zee et al., 1984 studied the effects of carbon monoxide, carbon dioxide and nitrogen on bacterial growth on meat under gas packaging. They used argon as a fully inert control. It was found that argon and nitrogen were equivalent in inhibition of anaerobes, and acted as inerting agents in inhibiting aerobes. Specifically, 4 strict aerobes, 3 anaerobes, and 12 facultative anaerobes isolated from meat were grown under carbon dioxide, argon, nitrogen, carbon monoxide, where argon was xe2x80x9cinertxe2x80x9d containing 10-70% nitrogen, carbon dioxide or carbon monoxide. Ar effect was found to be due strictly due to the gases in which it was admixed.
In the medical area, the noble gases are described as being useful in the preservation of living organs, cells, and tissues, primarily due to the high solubility and penetrability of the gases. For example, Ikegami et al., 1979, compare sperm motility and viability in nitrogen, argon, helium and carbon dioxide, where thermal factors are most important.
SU 507187 discloses improved preservation of bone transplants in a mixture of argon and formalin. The function of the argon is claimed as inerting.
In U.S. Pat. No. 4,008,754, preservation of isolated organs is described wherein helium or nitrogen or helium+xenan or helium+xenan+sulfur hexafluoride function equally well in preserving tissues in cooling. Similar results are described in Voss et al., 1970; SU 1289437; Ruile et al., 1971; Braun et al., 1973 (for freezing); Poppert et al., 1973. In the latter, organ preservation in hyperbaric xenon is described.
Thus, it is evident from the above that argon is perceived of and has been clearly described in both patent and in literature citations to be an inert and non-reactive gas, capable of affecting biological systems, such as food products, medical tissues, chemical reactions, enzymes, and food storage parameters only by means of displacing more active gases, such as oxygen. Thus, argon has been conventionally considered to be the equivalent of nitrogen as an inert and non-reactive gas, and is presently differentiated for use in the food industry solely based upon such commercial factors as cost, availability, and purity.
While a few literature citations are known in which it has been even suggested that argon and other noble gases may have properties unique for application to biological systems or food, each of these citations are different and clearly fail to teach or even suggest the conclusion upon which the present invention is premised.
For example, JP 52105232, (80002271), 1059647 describe the use of a gas mixture containing argon for preserving roasted chestnuts by retarding the growth of anaerobic molds, and extends this preservation to include rice cakes, bread, cakes in 80-20:30:70 argon:carbon dioxide, describing that this prevents growth of molds and anaerobic microorganisms. However, the data provided are self-conflicting, holding that neither high nor low levels of argon have effects, but that intermediate values do, in a simple experiment in which significant data are not presented, no tests or controls for oxygen levels were conducted, and no demonstration of the described anaerobicity of the molds tested was made. In fact, the data do not show an improvement for argon, and may be interpreted as simply proposing the substitution of argon for nitrogen as an inert and non-reactive gas.
JP 55111755 describes the preservation of cereals or vegetables in nitrogen+carbon dioxide, optimally containing also helium or argon (1-10 preferably 4-6% in the mixture) in 5-70% carbon dioxide in 95-30% nitrogen. This description is made to allow for the inclusion of noble gases as contaminants in other gases, however, the disclosed benefit of the noble gases is demonstrably impossible as reducing the content of the noble gas in the mixture cannot and does not improve the possible benefit. Further, described improvement in storage of cereals and vegetables (rice, onions, potatoes) preserved for long periods manifested itself by the suppression of budding. Argon and helium are described specifically to help color and glossiness. At the levels described, no improvement is possible, and even repetition of these experiments can show no effect.
Further, Manchon, 1978 studied preservation of bread and pastry in controlled atmosphere packaging. Poor results were obtained using nitrogen or argon or nitrogen+carbon dioxide. Good results were obtained using nitrous oxide or ethylene oxide+carbon dioxide. However, nitrous oxide is a reactive gas, and experiments carried out as described could only have substantiated argon to be inert and non-reactive.
U.S. Pat. No. 3,183,171 describes the control of fungal growth by noble gases. In particular, mixtures of carbon dioxide, carbon monoxide, oxygen, water vapor, or nitrogen with helium, xenon, krypton, neon, argon or a mixture of these, or a noble gas fraction constituting between three and ninety-five percent were used. Inhibition of growth rate is described for most mixes containing argon, xenan, krypton, or neon, while enhancement of growth rate is claimed when helium is added to certain mixtures. The very limited data were obtained solely for Neurospora crassa, as hyphal length increase over time.
U.S. Pat. No. 3,183,171 is based upon data presented Neurospora crassa. This patent did not demonstrate that hypha growth is equivalent to growth of the organism. By contrast, in accordance with the present invention; as will be described hereinafter, it has been discovered that enzymes responsible for fugal growth are inhibited and it is evident that the data of U.S. Pat. No. 3,183,171 describes effects for the control of hypha growth and not for the enzymatic control of microorganism growth. Thus, it is not possible from U.S. Pat. No. 3,183,171 for the artisan to comprehend that effective control of microbial growth is possible with noble gases.
As proof thereof, it is noted tha no application of practical utility in the control of microbial growth with noble gases has been made in the intervening twenty-five years.
Helium and high pressure application of various noble gases have been described as affecting the growth of bacteria (Fenn and Marquis, 1968, Thom and Marquis, 1979, Hegeman and Featherstone, 1969); protozoa (Sears et al., 1964), mammalian cells (Bruemmer et al.; 1967; Schreiner 1964, 1965, 1966 Nonr) and bacterial spore germination (Enfors and Molin, 1977). These results are cited in Schreiner, 1968 and Behnke et al., 1969). However, all of these reports provide inconclusive results and are difficult to interpret.
The use of nitrous oxide is described in U.S. Pat. No. 3,398,001, where during preparation and packaging of frozen avocados, freezing in nitrous oxide or nitrogen, followed by packaging in nitrogen using and oxygen level of  less than 2%, gave good preservational results.
A two-step treatment process for fresh fruits and vegetables is disclosed in EP 0422995 whereby nitrous oxide (10-100%) in admixture with oxygen and/or carbon dioxide is applied to vegetables for a time period in a first phase of treatment, followed by a separate second phase application of a gas mixture which contains nitrous oxide (10-99%) admixed with oxygen or carbon dioxide or nitrogen, which by action of the nitrous oxide then confers preservation. It is clearly described that nitrogen or argon are equally inert and non-reactive gases which may be freely used to complement in bulk any given gas mixture without effect.
Nitrous oxide has been shown to prevent ethylene formation and to provide significant fungistatic activity. For example, data are clearly presented in FR 2191850 proving the effective dissolution of nitrous oxide into the fruit/vegetable whereby it may be present to have an effect.
EP 0422995, AU 9063782, CA 2026847, ZA 9005704, FR 2652719, BR 9004977, JP 03206873, PT 95514 each describes a two-step treatment for preserving fresh vegetables by exposure at refrigeration temperature to an atmosphere of nitrous oxide and/or argon (other noble gases are specifically claimed to be inert) and optimally oxygen. Mixtures used variously include high titers of nitrous oxide, oxygen, carbon dioxide or nitrogen.
For packaging, a semipermeable membrane is described which has poor ability to retain argon. No controls were made, however, in the experiments for carbon dioxide or oxygen or nitrogen or argon, and no apparent action can be attributed to any gas except nitrous oxide.
The essence of each of these disclosures pertains to a two-step treatment process, not simple gas packaging, in which applied nitrous oxide or argon directly interferes with the production of ethylene by the fruit (tomatoes were tested). Argon is claimed to have specific utility in this regard, however, it is obvious from the data presented that the only effect of argon is to displace oxygen from the tissues of the fruit and thereby to limit respiration and thus ethylene production. The essential data presented in the figure purport to show a difference in ethylene production of air, nitrogen, argon and nitrous oxide which is precisely identical to their differences in solubility in the fruit (data given in EP 0422995 and below). In fact, this has been proven by duplicating the above experiment wherein adequate controls for solubility were made by inclusion of other gases, and finding that depression of ethylene is completely explained by oxygen displacement. Data are presented in FIG. 1 of the present specification.
Thus, the above descriptions of uses of argon in food treatment demonstrate only the inertness or non-reactivity of argon and merely confirm its ability as a non-reactive gas to displace air.
Addition of argon to a known mixture of carbon dioxide+oxygen is claimed in Schvester and Saunders. U.S. Pat. No. 4,946,326, EP 346201, PT 90762, AU 8936152, DK 8902755, BR 8902636, JP 2053435, ZA 8904258 to be effective in preservation of seafood and fish at 4xc2x0 C. The mixture comprises in partial pressure 5-68% carbon dioxide+5-20% oxygen+27-45% argon (preferably 50:20:30 carbon dioxide:oxygen:argon). The text describes the mixture as slowing down enzymatic and chemical reactions at the surface and inside fish and seafood products, as well as growth of some microorganisms such as fungus. No such data are presented, and no claim is made thereto. Other studies on such mixtures and such products find opposite results.
The results disclosed are not generally reproducible, and, in fact, are due entirely to careful control of processing hygiene, and the effects of carbon dioxide on microbes. The results presented are generally not significant and do not control for the known effects of carbon dioxide, oxygen and nitrogen alone or in mixtures without noble gases. It is clearly not apparent from the data disclosed that any observed effect is in fact due to argon or to the specific mixture claimed. The effects may be rationally be concluded to be due to the other components alone or in partial combination.
Moreover, EP 354337 describes an effect of carbon dioxide upon bacterial systems. Such effects are widely known and understood as being caused by the depressive effect of carbon dioxide upon ordinary repiratory processes, which cannot be interpreted as being specifically antienzymatic. The observed results in U.S. Pat. No. 4,946,326 can be largely attributed to the simple depression of respiration by carbon dioxide.
Additionally, JP 89/192663 describes the use of argon as an inert gas in the storage of liquors, while JP 88/51660 discloses the use of argon as an inert gas in the storage of mushrooms.
JP 87/108025 describes the use of a mixed gas including nitrogen, carbon dioxide, argon and nitrous oxide to store roasted chestnuts.
JP 70/66269 discloses a method of processing orange, lemon, group and pineapple juice and for preserving such juices by dissolving inert or non-reactive gases, such as nitrogen, argon and helium in the juice to a saturation level.
Thus, a considerable volume of literature exists generally relating to the gas packaging or gas saturation of foods. Some of this literature relates to the use of noble gases and inert gases in food packaging, using such gases as inerting or non-reacting agents equivalent to nitrogen. However, it would be extremely advantageous if a means were attained by which food substances could be preserved directly and not indirectly by mere oxygen displacement.
Accordingly, it is an object of the present invention to provide a method of preserving foods using at least one noble gas.
It is also an object of the present invention to provide various gas mixtures for effecting the above method.
It is further, an object of the present invention to provide a method for inhibiting enzymes which cause microbial organisms to grow in food and/or on food.
It is also an object of the present invention to provide a method for inhibiting enzymes produced by food which cause degradation thereof.
Moreover, it is an object of the present invention to provide a method for inhibiting enzymes secreted by spoilage microorganisms and/or on food.
Further, it is an object of the present invention to provide a method for inhibiting enzymes in and/or on food.
It is also an object of the present invention to provide a method for preserving color and/or appearance of a food product.
Also, it is an object of the present invention to provide a method for inhibiting non-enzymatic chemical oxidation reactions of a food product.
Moreover, it is an object of the present invention to provide a method for inhibiting chemical oxidative degradative reactions in food.
It is also an object of the present invention to inhibit oxidative degration of color in foods.
Moreover, it is also an object of the present invention to provide a method for preserving foods without using technologies which result in undesired changes in a food product, such as organoleptic, rheological, microbiological and nutritional changes.
Accordingly, the above objects and others which will become more apparent in view of the following disclosure are provided by a method of preserving a food by contacting the same with a noble gas, a mixture of noble gases or a gaseous mixture containing at least one noble gas.